Two-legged walding locomotion apparatus and its walking controller

ABSTRACT

A walk controller ( 30 ) for a biped (two-footed) walking mobile system, which drive-controls each joint drive motor ( 15 L,  15 R– 20 L,  20 R) of each leg portion ( 13 L,  13 R) of a biped walking mobile system based on gait data, includes a force detector ( 23 L,  23 R) to detect the force allied to a sole of each foot portion ( 14 L,  14 R), and a compensator ( 32 ) to modify the gait data from a gait former ( 24 ) based on the force detected by a force detector, and is constituted so that each force detector ( 23 L,  23 R) comprises at least three 3-axial force sensors ( 36   a,    36   b,    36   c ) allocated on a sole of each foot portion ( 14   L,    14   R), and a compensator (   32 ) modifies gait data based on the detected signals from three 3-axial force sensors ( 36   a,    36   b,    36   c ) which detect effective force, thereby the walk stability of a robot is realized, even on the unstable road surface condition with complex roughness.

TECHNICAL FIELD

The present invention relates to a biped (two-footed) walking mobilesystem, and more specifically to its walk control system which leads tostable walking.

BACKGROUND ART

A conventional biped walking robot generates the pre-designed walkpattern (hereinafter to be called “gait”) data, conducts walk controlaccording to said gait data, moves foot portions by the predeterminedwalk pattern, and thereby realizes biped walking.

However, such a biped walking robot tends to be unstable in walkingposture upon walking due, for example, to road surface conditions, orthe error of the robot's own physical parameters, or else, and maytumble down in some cases. On the other hand, if a robot is made toconduct walk control without pre-designed gait data while confirmingwalk conditions in real time, then walking is possible with stablewalking posture, but even in such cases, the robot may tumble down withcollapsed walking posture, when unexpected road conditions areencountered.

Therefore, what is called ZMP compensation is required, whereby thepoints on the sole of a foot of the robot where the composite momentumof floor reaction force and gravity becomes zero (hereinafter to becalled ZMP “Zero Moment Point”) are converged to the target value. Assuch a control method for ZMP compensation, the method to accelerate andadjust the robot's upper body by utilizing compliance control andconverging ZMP to the target value, as shown, for example, in JP5-305583 A, or the control method to adjust the landing position of therobot's foot is known.

Incidentally, in such control methods, the stabilization of a robot isaimed by ZMP regulation, and in said ZMP regulation there should be aprerequisite to accurately detect floor reaction force at a sole.

However, as for a biped walking robot of such structure, there may besuch cases where a whole sole does not land on the road surface in theunstable road condition with complex roughness, and floor reaction forceat a sole can not be accurately detected, and thereby ZMP compensationcan not be accurately conducted. For this reason, the robot's stabilitycan not be maintained, and the robot's biped walking becomes difficult.

DISCLOSURE OF THE INVENTION

It is the object of the present invention, taking into consideration theabove-mentioned problems, to provide a biped walking mobile system andits walk control system to realize walk stability by accuratelydetecting floor reaction force at a sole in the unstable road conditionwith complex roughness.

The above-mentioned objective is achieved in accordance with the firstaspect of the present invention with the biped walking mobile system,which comprises a main body having at both sides of its lower part apair of leg portions attached thereto so as to be each pivotally movablebiaxially, each of the leg portions having a knee portion in its midwayand a foot portion at its lower end, the foot portions being attached totheir corresponding leg portions so as to be pivotally movablebiaxially, the drive means for pivotally moving said leg, knee, and footportions, a gait former to form gait data including target angleorbital, target angle velocity, and target angle accelerationcorresponding to the required motion, and a walk control system todrive-control said drive means based on said gait data. Said walkcontrol system includes a force detector to detect the force applied onthe soles of respective feet, and a compensator to modify the gait datafrom a gait former based on the force detected by said force detector,and said force detector comprises at least three 3-axial force sensorsallocated on the soles of respective feet, and said compensator modifiesthe gait data based on the detected signals from three 3-axial forcesensors which detect effective force among respective 3-axial forcesensors of force detectors.

A biped walking mobile system in accordance with the present inventionis preferably provided with said main body which is the upper body of ahumanoid robot, and a head portion and both hand portions are attachedthereto.

A biped walking mobile system in accordance with the present inventionis preferably such that its respective 3-axial force sensor protrudesfrom a sole downward. Preferably, three 3-axial force sensors areallocated at three tops of an isosceles triangle on a sole of respectivefoot portion, or each 3-axial force sensor may be allocated on aperiphery of a circle with the center on the vertical drive axis of afoot portion on a sole of respective foot portion.

A biped walking mobile system in accordance with the present inventionis preferably such that its respective foot portion comprises an baseportion attached directly to the lower end of a leg portion, and a toeportion as a finger tip attached pivotally movably vertically to the endof said base portion, and each 3-axial force sensor of a force detectoris distributed on an base portion and a toe portion.

A biped walking mobile system in accordance with the present inventionis preferably such that one of its 3-axial force sensors is allocatednear an base portion, and another 3-axial force sensor is allocated nearthe tip of a toe portion, and still two other 3-axial force sensors areallocated left and right in the region near the border of an baseportion and a toe portion.

A biped walking mobile system in accordance with the present inventionis preferably such that said compensator automatically calibrates thedetected signals from each 3-axial force sensor by autocalibration.

The above-mentioned objective is also achieved in accordance with thesecond aspect of the present invention with the biped walking mobilesystem, which comprises a main body having at both sides of its lowerpart a pair of leg portions attached thereto so as to be each pivotallymovable biaxially, each of the leg portions having a knee portion in itsmidway and a foot portion at its lower end, the foot portions beingattached to their corresponding leg portions so as to be pivotallymovable biaxially, the drive means for pivotally moving said leg, knee,and foot portions. The walk control system of said biped walking mobilesystem drive-controls said drive means based on the gait data formed bya gait former including target angle orbital, target angle velocity, andtarget angle acceleration corresponding to the required motion, andcomprises a force detector to detect the force applied on the soles ofrespective feet, and a compensator to modify the gait data from a gaitformer based on the force detected by said force detector, and saidforce detector comprises at least three 3-axial force sensors allocatedon the soles of respective feet, and said compensator modifies the gaitdata based on the detected signals from three 3-axial force sensorswhich detect effective force among respective 3-axial force sensors offorce detectors.

A walk control system of a biped walking mobile system in accordancewith the second aspect of the present invention is preferably such thatits respective 3-axial force sensor protrudes from a sole downward. Alsopreferably, three 3-axial force sensors are allocated at three tops ofan isosceles triangle on a sole of respective foot portion, or each3-axial force sensor may be allocated on a periphery of a circle withthe center on the vertical drive axis of a foot portion on a sole ofrespective foot portion.

A walk control system of a biped walking mobile system in accordancewith the present invention is preferably such that said compensatorautomatically calibrates the detected signals from each 3-axial forcesensor by autocalibration.

According to said aspect, a drive means is drive-controlled by modifyingby a compensator the gait data from a gait former based on the forcedetected by a force detector comprising at least three 3-axial forcesensor allocated on a sole of each foot portion. In that case, when afoot portion lands on the road surface with complex roughness, the three3-axial force sensors protruding downward from a sole steadily contactthe road surface. Therefore, the stabilization of a main body, forexample, a humanoid robot's upper body can be maintained by accuratelymodifying the gait data based on the detected signal from three 3-axialforce sensors which detect effective force even on unstable roadsurface. Accordingly, even on unstable road surface with complexroughness, a sole of each foot portion of a robot can maintain thestability of a robot, and make possible steady walk control.

In case that three 3-axial force sensors are allocated at three tops ofan isosceles triangle on a sole of respective foot portion, two of the3-axial force sensors at the both ends of the bottom side of anisosceles triangle are in symmetrical condition, therefore the weightloaded on each 3-axial force sensor can be distributed evenly on leftand right, and each 3-axial force sensor can be easily calibrated.

In case that each 3-axial force sensor is allocated on a periphery of acircle with the center on the vertical drive axis of a foot portion on asole of respective foot portion, the torques around said vertical driveaxis are in the same condition, therefore the loads with respect to saidtorques can be evenly distributed to each 3-axial force sensor, and each3-axial force sensor can be easily calibrated with respect to thetorques.

In case that each foot portion comprises an base portion attacheddirectly to the lower end of a leg portion, and a toe portion as afinger tip attached pivotally movably vertically to the end of said baseportion, and each 3-axial force sensor of a force detector isdistributed on an base portion and a toe portion, when only an baseportion or a toe portion is in contact with the ground, each 3-axialforce sensor of a force detector can detect the floor reaction force ona sole.

In case that one of the 3-axial force sensors is allocated near an baseportion, and another 3-axial force sensor is allocated near the tip of atoe portion, and still two other 3-axial force sensors are allocatedleft and right in the region near the border of an base portion and atoe portion, when only an base portion or a toe portion is in contactwith the ground, three 3-axial force sensors of a force detector are incontact with the ground, and can accurately detect the floor reactionforce on a sole.

In case that said compensator automatically calibrates the detectedsignals from each 3-axial force sensor by autocalibration, even if thedetection accuracy is changed in respective 3-axial force sensor of aforce detector due to the surrounding temperature or ageing,autocalibration is conducted, and the floor reaction force can beaccurately detected by the detected signals from each 3-axial forcesensor of a force detector.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will better be understood from the followingdetailed description and the drawings attached hereto showing certainillustrative forms of embodiment of the present invention. In thisconnection, it should be noted that such forms of embodiment illustratedin the accompanying drawings hereof are intended in no way to limit thepresent invention but to facilitate an explanation and an understandingthereof, in which drawings:

FIG. 1 is a schematic view illustrating the mechanical makeup of a bipedwalking robot according to the present invention as one form ofembodiment thereof;

FIG. 2 is a block diagram illustrating the electrical makeup of a bipedwalking robot shown in FIG. 1;

FIG. 3 illustrates the allocation of a 3-axis force sensor allocated ona sole of each foot portion of a biped walking robot shown in FIG. 1,and (A) is the brief perspective view seen diagonally from the upperside, and (B) is the brief perspective view seen diagonally from thelower side;

FIG. 4 is a plan view of a sole illustrating the allocation of 3-axisforce sensors shown in FIG. 3;

FIG. 5 is a graph illustrating the allocation of each 3-axis forcesensor and the base position of force measurement shown in FIG. 4;

FIG. 6 is a flowchart illustrating the walk control motion of a bipedwalking robot shown in FIG. 1;

FIG. 7 is a plan view of a sole illustrating the first modified exampleof the allocation of a 3-axis force sensor shown in FIG. 3(C);

FIG. 8 is a plan view of a sole illustrating the second modified exampleof the allocation of a 3-axis force sensor shown in FIG. 3(C);

FIG. 9 illustrates the third modified example of the allocation of a3-axial force sensor shown in FIGS. 3(C), and (A) is a side view of afoot portion, and (B) is a plan view of a sole;

FIG. 10 is, in case of landing at a toe portion in a modified exampleshown in FIG. 9, and (A) is a side view of a foot portion, and (B) is aplan view of a sole;

FIG. 11 is a plan view of a sole illustrating the fourth modifiedexample of the allocation of a 3-axis force sensor shown in FIG. 3(C).

BEST MODES FOR CARRYING OUT THE INVENTION

Hereinafter, the present invention will be described in detail withreference to suitable forms of embodiment thereof illustrated in thefigures.

FIG. 1 and FIG. 2 show the makeup of an embodiment of a biped walkingrobot with a biped walking mobile system applied thereto in accordancewith the present invention. Referring to FIG. 1, a biped walking robot10 includes an upper body 11 as a main body having at both sides of itslower part a pair of leg portions 13L and 13R attached thereto, each ofthe leg portions having a knee portion 12L, 12R in its midway, and afoot portion 14L, 14R at its lower end.

Here, each of said leg portions 13L, 13R has six joint portions, namelyin the order from above, the joint portion 15L, 15R for the leg portionrotation of a waist (around z axis) with respect to the upper body 11,the joint portion 16L, 16R for the roll direction of a waist (around xaxis), the joint portion 17L, 17R for the pitch direction of a waist(around y axis), the joint portion 18L, 18R for the pitch direction of aknee portion 12L, 12R, the joint portion 19L, 19R for the pitchdirection of an ankle portion with respect to a foot portion 14L, 14R,and the joint portion 20L, 20R for the roll direction of an ankleportion. Each joint portion 15L, 15R to 20L, 20R is made up with a jointdriving motor. Thus, a waist joint comprises said joint portions 15L,15R, 16L, 16R, 17L, and 17R, and a foot joint comprises joint portions19L, 19R, 20L, and 20R.

Further between a waist and a knee joints, they are connected with thethigh links 21L, 21R, and between a knee and a foot joints, they areconnected with the lower thigh links 22L, 22R. Thus, the leg portions13L, 13R and the foot portions 14L, 14R at both sides, left and right,of a biped walking robot 10 have six degrees of freedom, respectively,and it is so made up to be capable of walking at will in a threedimensional space by drive-controlling these twelve joint portionsduring walk with respective drive motors at appropriate angles, and bygiving desired motions to whole leg portions 13L, 13R, and foot portions14L, 14R. Further, said foot portions 14L, 14R are provided with forcedetectors 23L, 23R on soles (bottom faces). Said force detectors 23L,23R are to detect, as described below, the forces on respective footportions 14L, 14R, especially the horizontal floor reaction force F.Here, said upper body 11 is illustrated like a mere box, but actually itmay be provided with a head portion or two hands.

FIG. 2 illustrates the electrical makeup of a biped walking robot 10shown in FIG. 1. In FIG. 2, a biped walking robot 10 is provided with agait former 24 to form a gait data corresponding to the desired motion,and a walk controller 30 to drive-control the drive means, that is, thejoint drive motors 15L, 15R to 20L, 20R of the above-mentioned jointportions based on said gait data.

Here, xyz coordinate system is used as that for a biped walking robot 10with x direction as anteroposterior direction (forward as +), with ydirection as horizontal direction (inner direction as +), and with zdirection as vertical direction (upper direction as +).

Said gait former 24 is to form the gait data including the target angleorbital, target angle velocity, and target angle acceleration ofrespective joint portions 15L, 15R to 20L, 20R necessary for the walk ofthe biped walking robot 10, based on the desired motion input fromoutside.

Said walk controller 30 is made up with an angle measurement unit 31, acompensator 32, a controller 33, and a motor control unit 34.

Into said angle measurement unit 31, the angle information of therespective joint drive motor is input by, for example, a rotary encoderor else, provided in the joint drive motor of respective joint portion15L, 15R to 20L, 20R, the angular position of respective joint drivemotor, that is, the state vector φ with respect to the angle and theangle velocity is measured, and output to the compensator 32. Saidcompensator 32 calculates the floor reaction force F based on thedetected output from a force detector 23L, 23R, modifies the gait datafrom the gait former 24 based on said floor reaction force F and thestate vector φ from an angle measurement unit 31, and outputs the vectorθi (i=1 to n, where n is the degree of freedom with respect to a robot10's walk) to the controller 33. Here, said controller 33 subtracts theangle vector θ0 at a robot's respective joint portion from the vector θias the gait data modified by the compensator 32, and forms the controlsignal of each joint drive motor, that is, torque vector τ, based on thevector (θi−θ0). Further, said motor control unit 34 drive-controls eachjoint drive motor according to the control signal from the controller 33(torque vector τ).

Here, since said force detectors 23L, 23R have a symmetrical makeup leftand right, explanation will be given for a force detector 23L onlyreferring to FIG. 3. In FIG. 3, the force detector 23L is made up, onthe bottom side of a sole plate 35 as the lower face of the foot portion14L, of three 3-axis force sensors 36 a, 36 b, and 36 c allocated at theboth sides of front rim and the center of rear rim.

Respective 3-axis force sensors 36 a, 36 b, and 36 c have the mutuallyidentical makeup, and, as shown in FIGS. 3(A) and (B), are made up toprotrude downward from a sole. Further, respective 3-axis force sensors36 a, 36 b, and 36 c are allocated, as shown in FIG. 4, at respectivetops of an isosceles triangle with a spired rear rim.

Respective 3-axis force sensors 36 a to 36 c have data fluctuation forrespective detected output, and the detected output varies by thesurrounding temperature or ageing. Consequently, the detected outputs ofthe respective 3-axis force sensors 36 a to 36 c are automaticallycalibrated in the compensator 32 by the auto calibration as explainedbelow.

First of all, explanation will be given to the calibration in thedirection of Z axis.

In FIG. 5(A), n 3-axis force sensors S1, S2, S3, - - - , Sn areallocated on a sole with respect to the origin of force measurementO(Ox, Oy). The origin of force measurement O is preferably agreed to thedrive coordinate system of, for example, the joint of a foot portion.Here, the position of respective 3-axis force sensor Si is assumed asSi=(X(i), Y(i)), and arbitrary three 3-axis force sensors, for example,S1, S2, and S3 are chosen out of the 3-axial force sensors S1 to Sndistributed as mentioned above, and their coordinate positions arerespectively assumed as S1=X(1), Y(1), Z(1), S2=X(2), Y(2), Z(2),S3=X(3), Y(3), Z(3).

The state of three point support is made so that the loads are appliedonly to said three 3-axis force sensors S1 to S3, and, as shown in FIG.5(B), arbitrary two 3-axis force sensors among the three, for example,S1 and S2 are connected with a straight line, and the cross point of theperpendicular line from the remaining one 3-axis force sensor S3 to saidstraight line is assumed as C.

Here, the center of gravity of the driven object is moved staticallyalong said perpendicular line from S3 to C, and then the voltage valuesoutput from S1 to S3 are measured. In this case, the more themeasurement points, the more accurate is calibration.

Assume f as the measured force, A,B as calibration parameters, V as thevoltage value at that instant, M as the total mass of the driven object,g as the acceleration of gravity, and k as the measurement point, thenthe relating equations are obtained. $\left\{ {{{\begin{matrix}{f_{{z{(1)}}k} = {{A_{1}V_{{z{(1)}}k}} + B_{1}}} \\{f_{{z{(2)}}k} = {{A_{2}V_{{z{(2)}}k}} + B_{2}}} \\{f_{{z{(3)}}k} = {{A_{3}V_{{z{(3)}}k}} + B_{3}}}\end{matrix}f_{{z{(1)}}k}} + f_{{z{(2)}}k} + f_{{z{(3)}}k}} = {{{Mg}f_{{z{(1)}}k}} = {f_{{z{(2)}}k}\left\{ \begin{matrix}{{{f_{{z{(1)}}k} \cdot {X(1)}} + {f_{{z{(2)}}k} \cdot {X(2)}} + {f_{{z{(3)}}k} \cdot {X(3)}}} = 0} \\{{{f_{{z{(1)}}k} \cdot {Y(1)}} + {f_{{z{(2)}}k} \cdot {Y(2)}} + {f_{{z{(3)}}k} \cdot {Y(3)}}} = 0}\end{matrix} \right.}}} \right.$

And, by assuming V, M, Y as known values and solving these equations asthe simultaneous equations of f, and by substituting the obtained resultinto the equation below, the required slope A of F/V straight line andthe intercept B are obtained at the same time. Further, by measuring ntimes, the calibration parameter for calibration can be calculated.${\begin{bmatrix}{\sum\limits_{k = 0}^{n}\; 1} & {\sum\limits_{k = 0}^{n}\; V_{{z{(i)}}k}} \\{\sum\limits_{k = 0}^{n}\; V_{{z{(i)}}k}} & {\sum\limits_{k = 0}^{n}\; V_{{z{(i)}}k}^{2}}\end{bmatrix}\begin{bmatrix}{B_{z}(i)} \\{A_{z}(i)}\end{bmatrix}} = \begin{bmatrix}{\sum\limits_{k = 0}^{n}\; f_{{z{(i)}}k}} \\{\sum\limits_{k = 0}^{n}\;{V_{{z{(i)}}k}f_{{z{(i)}}k}}}\end{bmatrix}$

Thus, the calibration in the direction of Z axis with respect to saidthree 3-axis force sensors S1 to S3 are completed. And, by choosingother different three 3-axis force sensors, repeating calculation of thecalibration parameters likewise, and conducting calculation of thecalibration parameters for all 3-axis force sensors, the calibration inthe direction of Z axis can be completed for all 3-axis force sensors.

Further, the method of calibration with respect to X and Y axes will beexplained.

First, as shown in FIG. 5(C), arbitrary two 3-axis force sensors, forexample, S1 and S2 are chosen out of the distributed 3-axis forcesensors S1 to Sn, and a robot's upper body 11 or the leg portion of theopposite side 13L or 13R are utilized, and thereby the momentum m aroundZ axis is generated. Here, F1=F2 for the forces F1 and F2 applied on to3-axis force sensors S1, S2, and momentum m is expressed by the equationbelow.m=F 1·√{square root over ((X(1)−X(2))²+(Y(1)−Y(2))²)}{square root over((X(1)−X(2))²+(Y(1)−Y(2))²)}{square root over((X(1)−X(2))²+(Y(1)−Y(2))²)}{square root over((X(1)−X(2))²+(Y(1)−Y(2))²)}

Consequently, forces F1, F2 applied on to individual 3-axis forcesensors S1, S2 are calculated, and the respective X and Y components areexpressed by the equation below. $\left\{ {\begin{matrix}{f_{x{(1)}} = {{{F1} \cdot \cos}\;\theta}} \\{f_{y{(1)}} = {{{F1} \cdot \sin}\;\theta}} \\{f_{x{(2)}} = {{{F2} \cdot \cos}\;\theta}} \\{f_{y{(2)}} = {{{F2} \cdot \sin}\;\theta}}\end{matrix},{\mspace{14mu}\;}{{{where}\mspace{25mu}\theta} = {a\mspace{11mu}{\tan\left( \frac{{X(2)} - {X(1)}}{{Y(2)} - {Y(1)}} \right)}}}} \right.$

On the other hand, the relationship between the voltage value V outputfrom respective 3-axis force sensors S1, S2 and the forces fx, fy isexpressed by the equations below, with k as the number of measurement.$\left\{ \begin{matrix}{f_{{x{(1)}}k} = {{A_{x{(1)}}V_{{x{(1)}}k}} + B_{x{(1)}}}} \\{f_{{x{(2)}}k} = {{A_{x{(2)}}V_{{x{(2)}}k}} + B_{x{(2)}}}} \\{f_{{y{(1)}}k} = {{A_{y{(1)}}V_{{y{(1)}}k}} + B_{y{(1)}}}} \\{f_{{y{(2)}}k} = {{A_{y{(2)}}V_{{y{(2)}}k}} + B_{y{(2)}}}}\end{matrix} \right.$

With these equation combined, and by measurements of n times, thedeterminants as shown below is obtained, and the calibration parametersA, B can be calculated. ${\begin{bmatrix}{\sum\limits_{k = 0}^{n}\; 1} & {\sum\limits_{k = 0}^{n}\; V_{{z{(i)}}k}} \\{\sum\limits_{k = 0}^{n}\; V_{{x{(i)}}k}} & {\sum\limits_{k = 0}^{n}\; V_{{x{(i)}}k}^{2}}\end{bmatrix}\begin{bmatrix}{B_{x}(i)} \\{A_{x}(i)}\end{bmatrix}} = {{{\begin{bmatrix}{\sum\limits_{k = 0}^{n}\; f_{{x{(i)}}k}} \\{\sum\limits_{k = 0}^{n}\;{V_{{x{(i)}}k}f_{{x{(i)}}k}}}\end{bmatrix}\begin{bmatrix}{\sum\limits^{\;}\; 1} & {\sum\limits^{\;}\; V_{{y{(i)}}k}} \\{\sum\limits^{\;}\; V_{{y{(i)}}k}} & {\sum\limits^{\;}\; V_{{y{(i)}}k}^{2}}\end{bmatrix}}\begin{bmatrix}{B_{y}(i)} \\{A_{y}(i)}\end{bmatrix}}\begin{bmatrix}{\sum\limits_{k = 0}^{n}\; f_{{y{(i)}}k}} \\{\sum\limits_{k = 0}^{n}\;{V_{{y{(i)}}k}f_{{y{(i)}}k}}}\end{bmatrix}}$

Thus, by simultaneously calculating the calibration parameters A, B inthe directions of X and Y axes, calibration can be made in the XY axisdirections.

Incidentally for the above-mentioned calibration, when respective 3-axisforce sensors 36 a to 36 c are allocated at the tops of an isoscelestriangle as shown in FIG. 4, the calibration parameters by calibrationhave the same value, since the 3-axis force sensors 36 a, 36 b allocatedat both ends of the front bottom side of the triangle are in symmetricposition left and right. Therefore, calibration can be easily conducted.

The biped walking robot 10 in accordance with an embodiment of thepresent invention is made up as described above, and its walking motionis conducted as described below according to the flowchart in FIG. 6.

In FIG. 6, first of all by the step ST1, the gait data is formed by thegait former 24 based on the desired motion (J=J) which is input, andthen is output to the compensator 32 of the walk controller 30. And bythe step ST2, respective forces are detected by force detectors 23L, 23Rprovided on both foot portions 14L, 14R, and are output to thecompensator 32. Also by the step ST3, the state vector φ of respectivejoint portions 16L, 16R to 20L, 20R is measured by the angle measurementunit 31, and is output to the compensator 32. By the step ST4 whichfollows, floor reaction force F is calculated by the compensator 32based on the detected output from the force detectors 23L, 23R. And bythe step ST5, the compensator 32 modifies the gait data based on saidfloor reaction force F and the state vector φ of respective jointportions 16L, 16R to 20L, 20R from the angle measurement unit 31, andoutputs θi to the controller 33.

Next by the step ST6, said controller 33 subtracts the angle vector θ0at a robot's respective joint portion from the vector θi and forms thecontrol signal of each joint drive motor, that is, torque vector τ,based on the vector (θi−θ0), and outputs it to the motor control unit34. And by the step ST7, said motor control unit 34 drive-controls thejoint drive motors of respective joint portions based on said torquevector τ. As a result, the biped walking robot 10 conducts walkingmotion corresponding to the desired motion.

After that, by the step ST8, the controller 33 makes J=J+1 by motioncounter increment, and waits for the pre-set sampling time, thereafterby the step ST9, if said J is below the pre-set motion finishing count,then the step is returned to ST2, and the above-mentioned motion isrepeated. And at the step ST9, if said J exceeds the motion finishingcount, then the motion is stopped.

In this case, for the biped walking robot 10 to drive-control each jointdrive motor, the gait data is modified in the compensator 32 based onthe horizontal floor reaction force F by the detected signal from each3-axis force sensor 36 a, 36 b, and 36 c of the force detectors 23L, 23Rallocated on the sole of each foot portion 14L, 14R, and the vector θiis formed, thereby a robot 10's stability can be attained with saidhorizontal floor reaction force F as regulation. Accordingly, even if arobot 10's each foot portion 14L, 14R, for example, each sole lands onthe unstable road surface with complex roughness, each 3-axis forcesensor 36 a, 36 b, and 36 c of the force detector 23L, 23R allocated onthe sole steadily lands on the ground, and can detect the horizontalfloor reaction force F, thereby the walking motion corresponding to therequired motion can be made surely possible.

FIG. 7 and FIG. 8 illustrate other examples of the makeup of each 3-axisforce sensor of force detectors 23L, 23R described above.

First in FIG. 7, respective 3-axis force sensors 36 a, 36 b, and 36 care allocated at tops of an equilateral triangle. According to suchallocation of 3-axis force sensors 36 a, 36 b, and 36 c, since theloaded weights on respective 3-axis force sensors 36 a, 36 b, and 36 care uniformly distributed, as well as acting similarly with the 3-axisforce sensors 36 a to 36 c in FIG. 4, the load is reduced on respective3-axis force sensors 36 a, 36 b, and 36 c.

In FIG. 8, respective 3-axis force sensors 36 a, 36 b, and 36 c areallocated at tops of an isosceles triangle like in FIG. 4, as well as ona single periphery with the vertical drive axis O with respect to legportions 13L, 13R of foot portions 14L, 14R as the center. According tosuch allocation of 3-axis force sensors 36 a, 36 b, and 36 c, they actsimilarly with the 3-axis force sensors 36 a to 36 c in FIG. 4, as wellas the torque calibration around said vertical drive axis O can beeasily conducted.

FIG. 9 to FIG. 11 illustrate still other examples of the makeup of each3-axis force sensor of force detectors 23L, 23R described above, and inthese makeup examples, each foot portion 14L, 14R comprises each baseportion 14La, 14Ra directly attached to each leg portion 13L, 13R, and atoe portion 14Lb, 14Rb as a finger tip pivotally movably attachedvertically to each base portion 14La, 14Ra. Here, toe portions 14Lb,14Rb may be actively pivotable with respect to base portions 14La, 14Raby drive means like other joint portions, or may be passively pivotable.

In FIG. 9, a toe portion 14Lb, 14Rb is provided with a 3-axis forcesensor 36 d at the position lopsided to the inner side of a tip, andrespective 3-axis force sensors 36 e, 36 f at the positions near bothends of a rear side, while a base portion 14La, 14Ra is provided withone 3-axis force sensor 36 g on the heel portion of its rear side.

On the other hand, the compensator 32 chooses the 3-axis force sensorwhich detects, for example, larger force based on the detected signal ofeach 3-axial force sensor 36 d to 36 g of a force detector 23L, 23R, andmodifies the gait data based on the horizontal floor reaction force bythree 3-axis force sensors 36 d to 36 g which detect effective forces.

According to such allocation of 3-axis force sensors 36 d, 36 e, 36 fand 36 g, if the base portion 14La, 14Ra of the foot portion 14L, 14Rcontacts the road surface, then, as shown in FIG. 9(A), three 3-axisforce sensors 36 e, 36 f, and 36 g, two 3-axial force sensors 36 e, 36 fallocated on the rear side of the toe portion 14Lb, 14Rb, and one 3-axisforce sensor 36 g allocated on the rear side of the base portion 14La,14Ra, contact the floor surface, bear the loaded weight as shown withthe hatched line in FIG. 9(B), and the horizontal floor reaction forceis applied from the floor surface. Therefore, the compensator 32calculates the horizontal floor reaction force based on the detectedsignals from the above-mentioned three 3-axis force sensors 36 e, 36 f,and 36 g, and modifies the gait data.

On the other hand, in case that only the toe portion 14Lb, 14Rb of thefoot portion 14L, 14R contacts the road surface upon the change ofwalking posture, as shown in FIG. 10(A), three 3-axis force sensors 36d, 36 e, and 36 f provided at the tip and the rear sides of the toeportion 14Lb, 14Rb contact the floor surface, bear the loaded weight asshown with the hatched line in FIG. 10(B), and the horizontal floorreaction force is applied from the floor surface.

Therefore, the compensator 32 calculates the horizontal floor reactionforce based on the detected signals from the above-mentioned three3-axis force sensors 36 d, 36 e, and 36 f, and modifies the gait data.Thus, even if the contacting state of the foot portion 14L, 14R on tothe floor surface is changed upon the change of walking posture, three3-axis force sensors 36 e, 36 f, and 36 g, or 36 d, 36 e, and 36 fdetect the effective force by receiving the horizontal floor reactionforce from the floor surface, and the compensator 32 can accuratelymodify the gait data.

In FIG. 11, as for each 3-axis force sensor 36 d to 36 g, by comparisonwith the case of FIG. 9, 3-axis force sensors 36 h, 36 i are eachallocated at both ends of a tip of the base portion 14La, 14Ra in placeof the 3-axis force sensors 36 e, 36 f allocated at both sides of therear end of the toe portion 14Lb, 14Rb, and a 3-axis force sensor 36 dof a tip of the toe portion 14Lb, 14Rb is allocated at about a centerwith respect to the left and right direction. Thus, 3-axis force sensors36 h, 36 i are allocated at each top of an isosceles triangle withrespect to a 3-axis force sensor 36 d or 36 g.

According to such allocation of 3-axis force sensors 36 d, 36 h, 36 iand 36 g, they act similarly with the 3-axis force sensors 36 d to 36 gin FIG. 9, and can conduct calibration easily for the middle 3-axisforce sensors 36 h, 36 i, and further, can be more firmly attached tofoot portions 14L, 14R by being attached to the base portions 14La, 14Rawhich is larger than toe portions 14Lb, 14Rb.

Here in FIG. 11, the middle 3-axis force sensors 36 h, 36 i are eachprovided to both sides of the tip of base portions 14La, 14Ra, but, notlimited to this case, may be provided to the connecting region of baseportions 14La, 14Ra and toe portions 14Lb, 14Rb.

Thus in case of the biped walking robot 10 according to the embodimentof the present invention, respective 3-axis force sensors 36 a to 36 c,or 36 d to 36 g, or 36 d, 36 h, 36 i, and 36 g of force detectors 23L,23R provided on the soles of respective foot portions 14L, 14R firmlyland on to the road surface with complex roughness. Consequently, bymodifying gait data based on the horizontal floor reaction force Fcalculated from the detected signal from each 3-axis force sensor, walkcontrol can be conducted with the horizontal floor reaction force Fgenerated from the friction of a sole with the floor surface asregulation, and the walk stabilization of the robot 10 can be achievedin the unstable road surface state with complex roughness.

In the above-mentioned embodiment, for example, in FIG. 4, FIG. 7, FIG.8, FIG. 9, and FIG. 11, 3-axis force sensors are allocated symmetricallyleft and right, but, not limited as such, it may be obviously anallowable case to be allocated at the tops of an inequilateral triangle.Also in the above-mentioned embodiment, 3-axis force sensors areallocated on the bottom side of a plate which makes up each sole, but,not limited as such, it may also be an allowable case that other plateis attached to the lower part of a 3-axis force sensor, and said 3-axisforce sensor is inserted between said plates. In this case, said 3-axisforce sensor can detect not only compressing force but also pullingforce.

Here in such a sensor structure, if each 3-axis force sensor, forexample, is allocated in even position on a sole, respectively, withrespect to the directions back and forth and left and right, forceamplification and calibration are easily conducted, as well as a sensorcan be most efficiently used.

Also in the above-mentioned embodiment, for example, in FIG. 4, FIG. 7,and FIG. 8, the force detector 23L, 23R is provided with three 3-axisforce sensor 36 a, 36 b, and 36 c, respectively, and in FIG. 9 and FIG.11, always three 3-axis force sensors 36 d, 36 e (36 h), 36 f (36 i), or36 e (36 h), 36 f (36 i), 36 g of the force detector 23L, 23R land onthe floor surface, but not limited as such, three or more 3-axis forcesensors may be provided, respectively. For example, as shown with abroken line in FIG. 4, two 3-axis force sensors 36 j, 36 k may beprovided in the middle region. In this case, the compensator 32 comparesthe detected signals of respective 3-axis force sensors 36 a, 36 b, 36c, 36 j, and 36 k, and chooses three 3-axis force sensors which detectlarger force, and may calculate the horizontal floor reaction force fromthe chosen three 3-axis force sensors.

Further in the above-mentioned embodiment, a compensator 32 modifies thegait data with the horizontal floor reaction force as regulation basedon the detected signals from respective 3-axis force sensors of theforce detectors 23L, 23R, but not limited as such, it may be obviouslyan allowable case to modify the gait data with ZMP regulation based onthe detected signals from respective 3-axis force sensors of forcedetectors 23L, 23R, as were the past cases.

Further in the above-mentioned embodiment, explanation was given to thecase where the present invention is applied to a biped walking robot,but not limited as such, it is obvious that the present invention isapplicable to a biped walking mobile system in which other variousmachines are supported on two legs, and said two legs make it possibleto walk.

INDUSTRIAL APPLICABILITY

According to the present invention as described above, a quite excellentbiped walking mobile system and a walk control system therfor areprovided, which can realize the walk stability by accurately detectingthe floor reaction force on soles of a robot, even in the unstable roadsurface condition with complex roughness.

1. A biped walking mobile system comprising; a main body, a pair of legportions attached thereto at both sides of its lower part so as to beeach pivotally movable biaxially, each of the leg portions having a kneeportion in its midway and a foot portion at its lower end, the footportions being attached to their corresponding leg portions so as to bepivotally movable biaxially, drive means pivotally moving each leg,knee, and foot portion, a gait former to form a gait data includingtarget angle orbital, target angle velocity, and target angleacceleration, and a walk controller to drive-control said drive meansbased on said gait data, said walk controller includes a force detectorto detect a force applied on a sole of each foot portion, and acompensator to modify the gait data from the gait former based on theforce detected by said force detector, wherein said force detectorcomprises at least three 3-axis force sensors allocated on the sole ofeach foot portion, and wherein said compensator modifies the gait databased on detected signals from three 3-axis force sensors which detecteffective force among respective 3-axis force sensors of the forcedetector.
 2. A biped walking mobile system as set forth in claim 1,characterized in that, said main body is a upper body of a humanoidrobot provided with a head portion and two hand portions.
 3. A bipedwalking mobile system as set forth in claim 1 or claim 2, characterizedin that, each 3-axis force sensor protrudes downward from a sole.
 4. Abiped walking mobile system as set forth in claim 1 or claim 2,characterized in that, three 3-axis force sensors are allocated at toppositions of an isosceles triangle on a sole of each foot portion.
 5. Abiped walking mobile system as set forth in claim 1 or claim 2,characterized in that, each 3-axial force sensor is allocated on a sameperiphery with the vertical drive axis of a foot portion as the centeron a sole of each foot portion.
 6. A biped walking mobile system as setforth in claim 1 or claim 2, characterized in that, each foot portioncomprises an base portion attached directly to the lower end of the legportion, and a toe portion as a finger tip attached pivotally movably upand down at the end of said base portion, and each 3-axis force sensorof the force detector is distributed and allocated in the base portionand the toe portion.
 7. A biped walking mobile system as set forth inclaim 6, characterized in that, one 3-axis force sensor is allocatednear a heel of the base portion, another 3-axis force sensor isallocated near a tip of the toe portion, and two other 3-axis forcesensors are allocated left and right in the region near the boundary ofthe base portion and the toe portion.
 8. A biped walking mobile systemas set forth in claim 1 or claim 2, characterized in that, saidcompensator automatically calibrates the detected signal from each3-axis force sensor by auto calibration.
 9. A walk controller for abiped walking mobile system to drive-controls drive means based on agait data including target angle orbital, target angle velocity, andtarget angle acceleration formed by a gait former corresponding to therequired motion, comprising; a force detector to detect the forceapplied on a sole of each foot portion, and a compensator to modify thegait data from a gait former based on the force detected by said forcedetector, wherein said force detector comprises at least three 3-axisforce sensors allocated on the sole of each foot portion, wherein saidcompensator modifies gait data based on the detected signals from three3-axis force sensors which detect effective force among respective3-axis force sensors of the force detector, and wherein the bipedwalking mobile system comprising a main body, a pair of leg portionsattached thereto at both sides of its lower part so as to be eachpivotally movable biaxially, each of the leg portions having a kneeportion in its midway and a foot portion at its lower end, the footportions being attached to their corresponding leg portions so as to bepivotally movable biaxially, the drive means pivotally moving each leg,knee, and foot portion.
 10. A walk controller for a biped walking mobilesystem as set forth in claim 9, characterized in that, each 3-axis forcesensor protrudes downward from a sole.
 11. A walk controller for a bipedwalking mobile system as set forth in claim 9 or claim 10, characterizedin that, three 3-axis force sensors are allocated at top positions of anisosceles triangle on a sole of each foot portion.
 12. A walk controllerfor a biped walking mobile system as set forth in claim 9 or claim 10,characterized in that, each 3-axis force sensor is allocated on a sameperiphery with the vertical drive axis of a foot portion as the centeron a sole of each foot portion.
 13. A walk controller for a bipedwalking mobile system as set forth in claim 9 or claim 10, characterizedin that, each 3-axis force sensor is uniformly allocated on a sole ofeach foot portion with respect to the back and forth direction and thehorizontal direction.
 14. A walk controller for a biped walking mobilesystem as set forth in claim 9 or claim 10, characterized in that, saidcompensator automatically calibrates the detected signal from each3-axis force sensor by auto calibration.